The present invention is directed to a process for applying nomenclature during formation of a printed circuit board which has a raised relief surface and which has soldered connections on a portion of electrical conductive paths or pad areas of the circuit board. Nomenclature refers to letters or symbols which, e.g., serve to identify a portion of the printed circuit board or serve to present certain information which is necessary or desirable to appear on the circuit board itself.
Nomenclature is conventionally applied in the manufacture of some circuit boards since identification or instruction which is legible on the board itself is desirable and in many instances essential. The current practice in the electronics industry is to employ ink screened films and a wet development step to apply such nomenclature to the surface of the printed circuit board. However the present invention relies upon dry film technology used in producing colored images on a substrate to provide this nomenclature in a process step immediately prior to application of molten solder to a circuit board protected by a solder-mask or nomenclature to which solder is not to adhere.
Chu et al. U.S. Pat. No. 3,649,268 discloses an image reproduction process using a photohardenable layer and a removable support involving the steps of lamination to a receptor, imagewise exposure to actinic radiation through the support to selectively raise the stick temperature of areas receiving the radiation, removal of the support, and application of a colored powder which adheres only to unexposed areas followed by repeating the above steps with another colorant.
Cohen et al. U.S. Pat. No. 4,282,308 discloses a dry film peel apart photosensitive element containing a strippable coversheet, a photoadherent layer and a tacky, nonphotosensitive contiguous layer receptive to colorant or particulate material and a support. The element is employed in color proofing in producing reversed toned or colored images and for duplicate colored images.
Taylor U.S. Pat. No. 4,489,154 discloses a process in preparing a surprint proof. A process is employed to apply different colored layers on a substrate to form a surprint proof employing a peel apart photosensitive element containing a strippable coversheet, a photoadherent layer containing a colorant, a tacky nonphotosensitive layer and a support. Exposure of the element through a separation negative and after separation the nonexposed from the exposed areas, a positive colored photoadherent image on the coversheet is adhered to a substrate or if exposed through a separation positive, a positive colored photoadherent image on the supported layer is adhered to a substrate. The process is repeated to form different colored layers on a substrate.